About packaging materials for food, medical supplies and others, and resin substrates of flat panel displays of liquid crystal, organic EL or the like, they are desired to have a high gas barrier property. From this viewpoint, known are gas barrier films wherein a metal such as aluminum or a metal oxide such as silicon oxide, aluminum oxide or magnesium oxide is evaporated on a polymer film substrate. Attention is paid in particular to a film wherein silicon monoxide is evaporated since the film has a high transparency and a high gas barrier property.
The evaporating material used to form such a silicon monoxide film is usually silicon monoxide produced by use of a vacuum condensing method. The vacuum condensing method is a method of mixing Si and SiO2 with each other in a starting material chamber, heating the mixture, and causing SiO to gas-phase-precipitate on the inner surface of a tubular condensing chamber connected to the upper of the starting material chamber, thereby producing SiO. The produced SiO is a dense precipitation. In some cases, this is cut away into a predetermined tablet form, and the tablet is directly used as an evaporating material. In other cases, the precipitation is once pulverized into powder, this is sintered into a predetermined tablet form, and the tablet is used. The case that the sintered body is used as an evaporating material is more frequently performed since the bulk density and other characteristic values can each be controlled into a wide range.
Meanwhile, one out of phenomena which become problems in the process for forming a silicon monoxide evaporated film is splash. This is a finely splashing phenomenon of a molten material. When this is caused in the formation of a film, pinholes and other defects are generated in the formed evaporated film so that the quality of the film falls remarkably. This phenomenon becomes more remarkable as the film-forming speed is made higher. Thus, this is a cause of suffocating the film-forming speed. For this reason, in the work for forming a silicon monoxide evaporated film, the restraint of the generation of the splash is an important technical theme. To attain this theme, approaches are being tried from various viewpoints. From the viewpoint of an evaporating material, attempts for improving the density or brittleness of the material, and other physical properties thereof are being made.
Specifically, about physical properties of evaporating material, it is considered that splash is less generated as the material is denser and harder. In accordance with this thought, Patent Document 1 describes a gas-phase-precipitation type silicon monoxide based evaporation material wherein the weight decreasing rate (rattler value) in a rattler test is 1.0% or less. About the powder-sintered type silicon monoxide based evaporating material, Patent Document 2 states that it is effective to make the bulk density as high as 1.60 g/cm3 or more by hot press at a high temperature and a high pressure.
Patent Document 1: Japanese Patent Application National Publication No. 2003/025246
Patent Document 2: Japanese Patent Application National Publication No. 2003/010112
Such an evaporating material having improved physical properties (dense and hard material) is less broken when used. Thus, the convenience for use is good. About the restraint of splash, however, advantageous effects to be expected are not attained in the actual circumstances.